Insulator



June 30, 19 c. D. CROSKEY EIAL 2,287,976

INSULATOR Filed June 27, 1940 5a UNDER CO RISSIN 4 2E u- BODY C PRES I 311mm (Z /D. (1 054? flaw' d efl/i wfi and Patented June 30, 1942 INSULATQR Carl David Croskey and Davidge Harrison Rowland, Baltimore, Md., assignors to Locke Insulator Corporation, Baltimore, Md., a corporation of Maryland Application June 27, 1940, Serial No. 342,798

4 Claims.

The invention herein set forth relates to a combination of insulator, glaze and sand so corelated as to the co-efllcients of expansion of the various elements as to produce an insulator body of greatly increased strength which is also provided with a sand grip by which the said body may be connected to either the co-acting insulator body or to a metallic member and by which connection the strength of the assembled unit or units is increased over that previously believed to be the maximum in such an assemblage.

In applicants co-pending application Ser. No. 267,349; filed April 11, 1939, now Patent No. 2,250,044 dated July 22, 1941, of which this application is a continuation in part, it has been pointed out that by the use of a sand formed from a percentage of Hanover ball clay and certain other ingredients it is possible to obtain a sand which will have a coefficient of expansion per degree centigrade ranging between 3.93 10 and 5 10 and it is pointed out in the Rowland Patent No. 2,157,100 that by using a ceramic glazing material having a coefiicient of expansion of 5.3 10- per degree centigrade with an insulator body having a coeflicient of expansion of 5.8 10- per degree centigrade, it is possible to greatly strengthen the insulator body. In fact, the combination of an insulator body with a compression glaze as set forth has increased the strength of the insulator bodygas much as one hundred percent (100%). a

In the co-pending application it has also been pointed out that by utilizing with an insulator body and glaze, as described in the Rowland patent, supra, an ordinary insulator sand generally formed by pulverizing fired ceramic material, the sand being applied to the coated insulator body while the glazing material is still moist, a gripping surface is formed but that such gripping surface materially weakens the insulator since the expansion and contraction of the sand particles differ in amount from the corresponding expansion and contraction of the glaze and the body, resulting in the formation of minute cracks by which lines of cleavage in the insulator are formed and through which the insulator often breaks when subjected to strain.

When, however, the novel form of sand, as set forth in our co-pending application, is applied in lieu of the ordinary insulator sand, said novel insulator sand (namely one in which the coefficient of expansion of the finished product is equal to or less than the coefficient of expansion of the glaze) greatly increases the strength of the insulator body by expanding at the same or a slightly lower rate than the glaze and thereby preventing incipient cracks in the glaze body with their deleterious eflects upon the insulator body.

In the drawing:

Figure 1 is a side elevation of an insulator embodying my invention with parts broken away to more clearly illustrate the invention, and

Figure 2 is an enlarged fragmentary sectional view of the insulator.

Referring more particularly to the drawing, l indicates the body of the insulator, 2 the glaze and 3 the sand through which the insulator body may be attached to metallic members or another insulator body 5 by the ordinary cement bond 4. The thickness of the glaze is greatly exaggerated in Figure 2 for the purpose of illustration.

In carrying out the invention the insulator bodies are formed from flint, potash feldspar, ball clay and kaolin or china clay in such proportions to to produce an insulator body which, when fired, will have a coeflicient of expansion in the order of 5.8 10 per degree centigrade. As an example of the proper proportions we prefer to use 24.4% of flint by weight, 30% of feldspar, 28% of ball clay, and 17.6% of kaolin or china clay.

The percentages for the glazing material are set forth in the Rowland Patent No. 2,157,100 but are here quoted for convenience:

Percentage by weight White Chocolate Coloring oxides The glaze so formed has a coeflicient of expansion in the order of 5 to 5.3x10 per degree centigrade and is extremely satisfactory for use with an insulator body having a coefficient of expansion in the order of 5.8 10 per degree centigrade.

The sand comprises a mixture of so-called Hanover ball clay with various oxides in relatively small proportions. The ball clay may, as

.5 per degree centigrade.

pointed out in our co-pending application, comprise 98.36% and we combine with this 1.64% of iron oxide of the formula F6203, which gives a coefiicient of expansion either of the mass or of the sand formed therefrom in the order of Hanover ball clay having a percentage by weight of the total mass of 98.04%, when combined with 1.96% by weight of manganese dioxide of the formula MnOz, gives a coefficient of expansion of the mass or of the sand of 4.75 10- And, as a further example, Hanover ball clay and, calcium carbonate, when combined in the percentage by Weight of 95.08 of the ball clay to 4.92 of calcium carbonate, gives a coeiiicient of expansion of either the mass or the sand of 3.93 10 per degree centigrade.

As pointed out in our co-pending application, this strange and unforeseen result is accomplished despite the fact that Hanover ball clay alone and any of the given ingredients alone have a coefiicient of expansion greater than the coefficient of expansion of the combined ingredients. Just why this phenomenon occurs we have been unable to determine but the fact remains that innumerable tests have shown the result always to be the same.

The resultant sand produced either by the vitrification of the mass and the subsequent grinding of the same or by the grir. .lg of the mass and the subsequent vitrification of the sand particles so formed produces a sand having a coeiiicient of expansion not greater than the coeflicient of expansion of the glazed body as herein described and the sand may be produced, if desired, having a materially lower coeflicient of expansion than the glazed body.

Utilizing the respective ingredients above described to produce an insulator body, a glazing material and a sand, the insulator body is then either dipped in or sprayed with the glazing material and while the glazing material is still moist a sand band or a plurality of sand bands are applied to the insulator body and are caused to adhere to the same by reason of the moist glazing material. The body is then fired as usual under proper control and after the body has been fired so as to completely vitrify thesame and to form a vitrified ceramic glaze coating over the same through which the sand particles project, it is found that the sand has fused to the insulator body and become in eifect an integral part thereof. The insulator body is then connected either to metallic members or to another insulator body by utilizing the ordinary cement bond and it is found that upon the hardening of the cement the assembled unit possesses strength far in excess of such units where the ordinary porcelain sand formed by grinding the ordinary porcelain body is utilized.

It is our belief that by the use of a sand having a coeflicient of expansion not greater than the coefficient of expansion of the glaze or less than the coeflicient of expansion of the glaze that upon the expansion of the body, meaning the entire insulator, the sand acts to prevent incipient cracks forming in the glaze and hence prevents the formation of cleavage lines upon which former insulators broke at or adjacent the sand band.

In our co-pending application we have claimed the sand per se and we make no claim to the sand per se in this application, claiming only the entire combination of insulator, glaze and sand as is set forth in the appended claims.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

1. The combination with an insulator body of ceramic material having a coefiicient of expansion in the nature of 5.8 to 6X10- of ceramic glazing material therefor, said glazing material having a coefiicient of expansion in the order of 5.3x 10- per degree centigrade, a band of ceramic sand applied to the insulator body after the same has been coated with said ceramic glazing material, said sand having a coefficient of expansion less than 5.3 10- per degree centigrade, said body, glaze and sand being adapted to be vitrified simultaneously.

2.- The combination with an insulator body of vitrified ceramic material having a coeflicient of expansion in the order of 5.8 10- per degree centigrade, of a vitrified ceramic glaze covering the exterior portion of said body, said glaz having a coeflicient of expansion substantially less per degree centigrade than the coefficient of expansion of said insulator body, and a band of ceramic sand surrounding a predetermined portion of said insulator body and fused thereto, particles of said sand projecting outwardly from adjacent portions of the insulator body, said sand being vitrified and having a coeliicient of expansion per degree centigrade less than the coefiicient of expansion of said vitrified ceramic glaze.

3. The combination with an insulator body of ceramic material having a coefiicient of expansion in the nature of 5.8 10 per degree centigrade, of a glazing material therefor, said glazing material having a coefficient of expansion less than the coeflicient of expansion of the body of said insulator, a band of sand applied to the insulator body after the same has been coated with said glazing material, said sand having a coeflicient of expansion not greater than the coeflicient of expansion of the glazing material, said body and glaze being adapted to be vitrified simultaneously.

4. The combination with an insulator body of vitrified ceramic material having a coefficient of expansion in the nature of 5.8 10 per degree centigrade, of a vitrified glaze covering the exterior portion of said body, said glaze having a coefiicient of expansion substantially less than the coeilicient of expansion of said insulator body, and a band of sand surrounding a predetermined portion of said insulator body, particles of said sand projecting outwardly from the adjacent portions of said insulator body, said sand being vitrified and having a coeiiicient of expansion not greater than the coefficient of expansion of said glaze.

CARL DAVID CROSKEY. DAVIDGE HARRISON ROWLAND. 

